Final Program - Society for Risk Analysis

four cases of multiple myeloma were identified among this subset. However, the coloncancer data suffer from neither of these limitations. Based on a well-documentedretrospective exposure assessment, linear regression of the categorical data is usedhere to estimate an upper bound worker risk of over 0.1 per mg/m3 exposure. Thesedata suggest inhalation of MBT may pose a risk for colon cancer, but further studiesare needed to corroborate this and to determine if MBT exposure increases the riskof developing other cancers. “The views expressed are those of the authors and donot reflect the views or policies of the USEPA.”T3-B.4 Weir MH, Razzolini MTP, Rose JB, Masago Y; weirma@msu.eduMichigan State UniversitySTOCHASTIC MODELING OF WATER RECLAMATION TREAT-MENT REDESIGN SUGGESTIONS ADDRESSING CRYPTOSPORIDI-OSIS RISK AT A RECREATIONAL SPRAY PARKThis study is aimed at modeling a water reclamation treatment system for a recreationalspray park that experienced a significant cryptosporidiosis outbreak, usingmicrobial risk assessment. In this case the spray park’s water reclamation treatmentsystem was modeled using a Markov chain model to develop a distribution of theoocyst concentration exiting the water reclamation system and being sprayed ontothe recreation surface. Probability distributions were then fitted to the output fromthe Markov chain model and used for the Monte Carlo method to model the riskof cryptosporidiosis infection to spraypad users. The water reclamation treatmentsystem used during the time period of the outbreak (filtration and chlorination) wasmodeled, then the estimated risk level for this configuration was compared to two engineeringdesign retrofits that have efficacy potential for Cryptosporidium (ultravioletand ozone treatment). In addition to the supplemental treatment steps, the removalof a design flaw that allows for a portion of the water from the spraypad to bypassthe treatment system was modeled alone and in tandem with the additional treatmentoptions. An epidemiological study of the outbreak demonstrated that the likeliestcause of the outbreak was a bolus fecal release from a person recreating on the spraypad.Therefore this is the scenario that has been modeled. The results show that theremoval of the bypass pipe, reduced the risk of infection appreciably, however, largerrisk reductions were experienced with the additional treatment steps. While there isremaining risk due to the scenario (fecal release in the recreating area), removal of thebypass pipe is the minimum recommendation. We will present a stochastic modelingframework of water treatment systems via a mass balance approach, which is thenincluded in a stochastic risk modeling framework to inform potential design changesimproving human health protection.192T3-3.4 Weir MH, Shibata T, Masago Y, Cologgi DL, Rose JB; weirma@msu.eduMichigan State UniversityQUANTITATIVE MICROBIAL RISK ASSESSMENT OF FOMITES AC-COUNTING FOR SURFACE SAMPLING EFFICIENCY FOR VIRUSESAND NON-SPORE FORMING BACTERIAQuantitative microbial risk assessment (QMRA) has demonstrated itself asa vital tool in assessing response and optimal mitigation actions from a release ofpathogens in the indoor environment. There exist however significant data gapspreventing a greater understanding of the interaction between potential host and theindoor environment. One of the major gaps is a greater understanding of the interactionbetween; fomite (inanimate surface capable of harboring pathogens), humansand pathogens. This study was initiated to investigate the recovery efficiencies fromvarious non-porous fomites for a virus surrogate, bacteriophage P22 and a non-sporeforming bacteria, non-pathogenic Staphylococcus aureus (S. aureus) and to model theeffect of this recovery efficiency on the associated risk estimates. The scenario used isa shared office where the first user contaminates the fomites in the office (non-porouscommon office fomite surfaces) with a virus and bacteria, hypothetically similar to influenzaand pathogenic S. aureus for this hypothetical scenario, then two subsequentpeople use the office for 4 hour intervals separately. Two forms of the nested Markovchain models are developed, one where the transfer efficiency is included directly inthe loss rates and the second where the transfer efficiency is neglected from the lossrates, such as is performed in current risk estimates. The results of the Markov chainmodels are used to fit probability distributions for the Monte Carlo method invokedfor the risk estimation. Preliminary results show a significant difference in the riskestimate given the inclusion of transfer efficiency. Sensitivity analyses signify thatwhile initial concentration to the fomites still remains the most significant effect onthe estimated risk, inclusion of the transfer efficiency greatly reduces the risk model’ssensitivity to the initial concentration.M4-C.4 Wheeler JS, Worley RR, Ruiz P, Satarug S, Fowler DA; jzw1@cdc.govAgency for Toxic Substances and Disease Registry, University of Queensland School of Medicine,AustraliaENHANCING THE AGENCY FOR TOXIC SUBSTANCES AND DIS-EASE REGISTRY’S (ATSDR) SITE ASSESMENTS WITH PHARMACO-KINETIC MODELS AND BIOMONITORING DATAOne of the key missions of the ATSDR is to assess the human health impactof contamination at waste sites, industrial sites, and even from toxicants resultingfrom natural processes. Assessment of the human health impact of toxic substancesrequires high quality toxicity information and exposure data. In several instances environmentalexposure data may not exist but biomonitoring data (e.g. blood lead levels)are available. In the case of blood lead levels a direct comparison can be made to a